Detailed genetic and physical maps for the mouse will be essential for supporting and annotating sequence maps. Community backcross and radiation hybrid mapping resources that provide common mapping reagents and associated databases provide the underpinnings to construct these vital reference maps. The primary objectives of this project are 1) to maintain the existing DNA panel mapping resource that supports the development of a high quality, high density genetic map and its associated database, 2) to further develop and support a community database for RH mapping in the mouse and 3) to judiciously map loci that will provide additional cross-referencing between the genetic and radiation hybrid maps that ultimately will allow their integration.